Recoverable errors:
Recoverable errors do not cause data loss, so I report an amber warning state to indicate that a retry was required to get the data. Retries will increase the disk service time.

Predictive failure analysis:
This state is reported back from the disk drive itself; I think it means that the disk has not yet had a problem, but it will have one soon. Therefore, I report a red problem state and tell you to get a new disk before it fails on you.

Device not ready:
The device has gone offline, or perhaps it has died completely. The SCSI bus has become disconnected, or the Fibre Channel laser has died. I report a black state, as the disk is down. Check power and cables then try replacing the disk.

Media error:
The media is the surface of the disk, so a media error is often caused by a head crash or misalignment due to overheating. This is a black state, as a new disk is required.

Illegal request:
An illegal request could be caused by corruption of the command, or by a software bug. I report a black state, but I’m not sure what to do about it.